Learning the Science of Deduction
by StormLeviosa
Summary: Batman has earned the title of 'World's Greatest Detective' but who held it before him? Sherlock Holmes, according to the Gotham by Gaslight universe. (Taken from that one line: "as my mentor once told me, 'when you have eliminated the impossible, whatever remain, however improbable, must be the truth,'" which canonically implies Sherlock Holmes was Bruce Wayne's mentor.)


**Author's Note:**

This is just a random one shot based on one line from one movie: 'Gotham by Gaslight.

I did way too much research on Victorian slang and the Anglo-Afghan wars while writing this but who cares about homework anyway, not me apparently. I also wasn't planning on writing any more for this crossover but I got fed up of Biology revision and wrote a sequel. It's called 'Fly by Night' and I will upload at some point soon.

A word of warning, I have only read two of the Sherlock Holmes books (the Arthur Conan Doyle versions): A Study in Scarlet and the Hound of the Baskervilles, only one of which is relevant to this story so I had to do more research on the rest so I could write.

Very, very self-indulgent and may not make much sense without having seen Gotham by Gaslight (which everyone should if you haven't already because it's great). Please, let me know what you think in the reviews and I may reply because I love reading all them.

 **Edit:**

This is the updated version because something went wrong the first time. I have had so many issues with this document it's unreal but I won't get into that now. Thanks so much to xDarklightx who figured it out and let me know because otherwise I wouldn't have had a clue. This is for you.

Learning the Science of Deduction

Bruce Wayne arrived in London from Afghanistan with little idea of why. He supposed it was a lucky coincidence on his part that England (or, more specifically, British India) was at war with the Emirate of Afghanistan and that it was them and not the afghan army that had found him injured in the desert after an intense battle. How the regiment was asinine enough to believe him one of them was anyone's guess but they had got him back to civilisation when he was injured and near death so he could only thank the Lord for small mercies. Now, however, he was alone in a strange city and although he had money in spades but there wasn't any way for him to use it without arousing suspicion. He had entered England as John Watson after all.

Stamford was a doctor and a bloody good one if he was being honest. Some of his enthusiasm for the man may have come from him being so willing to indulge in his flights of fancy and pretend to be old friends for the duration of their meal while giving him information critical to his inevitable prolonged stay in London. An old acquaintance of Stanford's was mentioned in passing with regards to his current accommodation crisis and he pounced upon the opportunity with as much rigour as he could convey without looking suspicious. His luncheon completed and new friend brought irrevocably to his side, they departed the Criterion for St. Bartholemew's hospital: Stamford's workplace.

They found Holmes in the laboratory. He was a dark haired man, tall and slim, with a tobacco pipe hanging from his mouth and a cane resting against the edge of the bench. He was conducting some form of experiment and appeared so oblivious to his surroundings that he had not noticed their entrance. Stamford, for all his charitable kindness, did not know his 'acquaintance' nearly as well as he had implied over lunch and his bluster to make up for his lapse only made Bruce cringe. Holmes turned to him, ignoring Stamford, and looked him over from head to toe and back again before shaking his hand with a firmness that was surprising for someone of his stature. Then he said with a voice cold and dispassionate: "you have been in Afghanistan, I perceive." He should have known Holmes was a detective.

The Baker Street apartment was large for such an abode in central London. The bedroom Bruce had claimed for his own was large and comfortable, though far smaller than any in Wayne Manor with the possible exception of Alfred's which he had refused to move from (Bruce had argued against this for two days before the butler had reminded him that as heir to the Wayne fortune and a prominent figure in high society he had to maintain appearances). The living room was of a size approximate to Wayne Manor's drawing room with tall, broad windows and cheerfully furnished. The fireplace took up the majority of one wall and dark varnished bookshelves lined another. It was a warm but airy and seemed almost more reminiscent of a library or study than a living room but Bruce did not quite dare to reveal himself by committing such a blunder as to tell Holmes so. Holmes was not going to be an easy man to live with without him knowing who he really was. He needed to learn Holmes' tricks.

A consulting detective! Of course, Holmes would belong to such a riveting and admirable profession. That he had invented the position only increased Bruce's approbation of the man. And there was a crime to solve! Perhaps his impromptu trip to London was not worthless after all. Perhaps he would learn something yet.

It was a fascinating thing, to watch Holmes at work. His intellect was something so far removed from the general populace, from the character Bruce was playing, that seldom could anyone follow his reasoning. Bruce managed, though not without some difficulty and a period of adjustment. Holmes seemed unsurprised by his ability to both appreciate and match his mental gymnastics and took Bruce on as his apprentice, though to everyone else he remained only his staunchest companion and loyal lapdog. There was something exhilarating about the casual deception Holmes had initiated that appealed to Bruce. In the far corners of his mind devoted to the shadowed, crime-ridden streets of Gotham he began to devise a plan. He could remove the threat that had haunted Gotham's streets since its formation. (Of course, he would be breaking the law every time he left the manor and his place among Gotham's elite would be forfeited but what was his deception of Holmes for, if not practise?) He wrote home for the first time since his departure, informing Alfred of his whereabouts and of his plan, still in the earliest stages of construction.

The years passed as he supposed they were wont to do and Bruce stayed with Holmes, maintaining their charade for the benefit of London society. It was in 1888, seven years after his arrival in London that Mary Morstan came to their door. Her case was invigorating in a way that only a Holmes-worthy case can be and it didn't harm that Miss Morstan was far more attractive than the facetious women of Gotham's upper class. Even Holmes was not predisposed to despise her which was no small feat on her part. He claimed she had a 'decided genius' and her independence in the face of her situation was gratifying: neither Bruce nor Holmes had any need to watch over her while investigating. Bruce wondered if his admiration of her was love as they grasped hands instinctively at the sound of Mrs Bernstone's whimpering.

Holmes' deduction was suitably outrageous and Bruce was, for the first time, entirely too skeptical of his mentor's conclusion. Tempers ran high and then Thaddeus was arrested and Holmes seemed far too at ease with the situation. His dismissal of anything but the case, of others' well-being, of Batholomew's murder, irked Bruce and his explanation was so fantastical that Bruce could hardly believe it. But he believed in Holmes. He believed Holmes' reasoning. He believed Holmes knew what he said he knew. He believed all this because at his core Holmes was so brutally honest, so unswervingly loyal, so firm in his convictions, that he could not lie to Bruce. It was a failing of his, perhaps his only failing, that he had taught his student to eclipse the master. So, his explanation: "when you have eliminated the impossible, whatever remains, however improbable, must be the truth" was more than enough to satisfy.

It was shortly after this, when Bruce announced his intention to marry Mary, that he argued with Holmes, though not for the first time, most reprehensively. Their friendship now at an end, he left Baker Street with a driving rain falling through the smog that eventually hid his erstwhile home from view.

Mary was a charming companion for him as he prepared for his departure from England. He knew that he was really only tot-hunting, searching for a pretty woman to seduce and practice his charms on, hone his deception. He felt no shame in stringing her along in such a way, only regretted that he would have to leave her company if he was ever to return to America. He falsified an urgent telegram informing him of an elusive American relative's unfortunate demise and left promptly for Gotham on the next ship to cross the Atlantic.

Despite the dramatic end to their friendship, Bruce remembered Holmes' teachings. Batman was, first and foremost, a detective and the skills he had so artfully employed among London's criminal underworld were even more applicable in Gotham. Crime was a constant in Skinners End and 'Jack the Ripper' was not the first nor the last criminal to stalk the shadowed alleys at night. He was the first to challenge Batman's might, however. Sister Leslie's death was an unforeseen and terrible consequence of his arrogance. He had become complacent. He needed someone to remind him of his mortality, to keep him from plunging over the edge of the abyss in his relentless pursuit of justice. He should not have left Mary in London. By the time of the Ripper's death, he had Selina for company and before he could get his head around _that_ he had three little boys, all orphans like him, to look after too (he had no doubt in his mind that such a contumacious woman as Selina would not hold with such nonsense as societal views of marital roles). One day, perhaps they would wish to join him in his unceasing crusade against the smothering darkness of Gotham though he wished they wouldn't. Donning the cape and cowl would end the youthful vitality that spurred them on, would undo all the progress they had made with their induction into Gotham high society. But for now his little family, the result of benevolent Bruce Wayne spilling over into apathetic Batman, would keep him from harm.


End file.
